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Intel Core i7-875k and i5-655k processor review

Rating: 9.0.

KitGuru has been overclocking since speeds were measured in MegaHz. In all those years, we’ve never seen a chip taken to 5GHz on air. Never. Until now.

After the FX fell to Conroe, Intel has dominated the performance CPU market for many years. AMD’s eggs are all in the Fusion basket and not expected to be hatched until Q2 2011.

However, one valiant design group managed to deliver the Thurban, 6-core Phenom II X6 product range to market (purely as a stop gap). The unlocked Black Edition 1090 went some way to appeasing AMD’s die-hard fan base.

Unfortunately, that launch seems to have stirred a beast. That beast has an R&D budget bigger than the GDP of many small nations. It has a marketing operation that makes ‘wet ice on wet ice’ look sticky. And it has enormous engineering muscle. All of those advantages have been thrown into creating the ‘special K’ edition processors for l33t enthusiasts who want crazy-clocks delivered for meagre-money.

Having spent days testing the Core i5 655k and Core i7 875k in our labs, KitGuru feels confident in saying… OMG.

Unfortunately for AMD, Intel's processors not only offer more computational performance via smaller silicon per clock cycle, its chips also consume less power while doing so.

Intel has the edge. Several edges, from the design stage to final manufacturing. Although, in my opinion, they have also been lax in targeting specific sectors. Relying on a ‘one size fits almost all’ approach. Until now.

As we opened the two little processor boxes, we could almost hear the bell in the background.

Unlocked cores?   Unlocked multipliers?
Wake up Phenom X6.
Ding, ding. There’s a new challenger in the ring.

The Core i5-655k is an unlocked version of the Core i5-650 and the Core i7-875k is an unlocked Core i7-870. These K Series versions are linked to identical core clocks, thermal dynamics and Turbo frequencies as their locked counterparts. The edge however is in the fact that you can adjust the memory and core multipliers on the fly.

Furthermore if we told you the 875k was actually cheaper than the 870k would your ears prick up? No, I am not kidding because the UK pricing is looking to be around £299 inc vat for the unlocked 875k with the locked 870 still costing around £420. While we would expect the price of the 870 to drop soon it just proves that Intel really have taken off the gloves.

With so many processors in the current line up, lets do a little recap to get things clear in our head.

Base core clock speed
Peak turbo clock speed
L3 cache size
Memory channels
Core i5-650
4 MB
Core i5-655k
4 MB
Core i5-661
4 MB
Core i5-670
4 MB
Core i5-680
4 MB
Core i5-750
8 MB
Core i7-860
8 MB
Core i7-870
8 MB
Core i7-875K
8 MB

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  1. Man that 875k is sweet as anything Intel have made. Can’t wait.

  2. What a great bunch of processors – really nice overclocking capabilities, they are bound to be popular.

  3. £300 is still a lot of money for a processor, although it is good to see the prices being lower, since the 870, as its considerably more and is basically the same deal just locked. nice overclocks, that noctua cooler is pretty hefty looking, must weigh a ton.

  4. When are they released? I see no mention of them on any stores locally here.

  5. I was impressed with the 6 core AMD chip too, that gives solid performance especially in the encoding tests.

  6. It will be interesting to see the new upcoming black editions also. I would like to see how they perform.

  7. All Intel is doing is killing it’s enthusiast platform, AMD will counter with a price cut to the black edition and the value equation will change again.

  8. Bought a i5-750 in november, it is still in its unopened box (because of unexpected cash shortages for the rest of the built), but happy to see that processor is still a good value 6 month later.

  9. Bought a i5-750 in november, it is still in its unopened box (because of unexpected cash shortages for the rest of the built), but happy to see that processor is still a good value 6 month later.

  10. I’m glad you like the 875k but only benchmark junkies will be purchasing it.
    most people purchase a computer for work or for video games and this does not fit the bill for either of those.

  11. I still lament the absence of the x4-955, from a value perspective, but in the grand scheme I think it makes little difference.

    AMD really, badly, urgently needs to get its next gen CPU out, and have it be impressive or at least more competitive.

  12. My next build will probably still be Thuban-based, so I don’t get locked into a dead platform like I did with LGA775 and my Wolfdale.

  13. (HD) Destrotor

    Ouch, this was a pretty serious hit to AMD. Not a fatal, but serious blow.

  14. I love the competition, its already forcing intel to drive down prices. cant beat it!


  16. overclockers will love these, what are you talking about. 980x is 3 times the price of the 875k. idiot

  17. This type of product release is what I call marketing to “generate sales with new customers, to crap with our existing customers.” I would not suggest that if they priced this i7-875 where it ideally “should be” in the Intel lineup, but they have not.

  18. Haha to all the AMD fans here, in your face 🙂

  19. Hey, to the idiot who said the 980x is faster. get a brain man, its the price of a car. the 875k isnt far off the performance if you overclock it to the max. ive ordered one based on this review. cant wait, now I just need to upgrade my cooler. will report back with my findings

  20. I need to order the 655k, it will do me nicely when I overclock, hope to get 4.4ghz out of it 🙂 thanks fo the great review

  21. shit i was more impressed with the cooler than the processor, gotsta get me one of those.

  22. if I had bout a 975 extreme perhaps I would be regretting that purchase now but I am totally satisfied with my AMD, even now. My computer is still waiting for a current Generation game that can push it’s limits, so I am totally cool with waiting till next spring for a new processor which hopefully will set new standards.

  23. Better to buy mainstream MB/CPU/RAM for $300 or less (i.e. AMD 630, 765G MB, 4GB RAM) once every two years than try to buy a future-proof $600 system every four (i.e. i920 + 1366 MB + 6GB RAM).

  24. Ironically, the best parts to invest in are probably Case+PS+Monitor since you can carry them from build-to-build for the most part.

  25. what a brilliant review zardon, thank you very much. great help for my next system

  26. I also wonder if unlocked multi’s really lead to extraordinary overclocking advantages.

  27. I don’t see how they are killing the enthusiast platform that title belongs to Socket 1366 not 1156 which is the mainstream platform, if they release a i7 900 series chip that is unlocked and undercuts the x980 then you might have a point.

  28. really all this does is benefit the novice overclocker for intel processors but at the same time it removes the headache of dealing with memory timing.. especially if your right at the edge of using ddr3 1600 or getting stuck having to run it at ddr3 1400 or 1500 because your ram wont run above ddr3 1600 due to the blk being raised.. but in all honesty i think they are to late to the show with these processors.. they should been released around the same time as the locked versions.. AMD still has the better business model with their locked and unlocked processors by leaving all the high end versions unlocked and not charging an insane premium for them either.. while leaving all the low end versions locked so theres no way to get confused about what your buying..

  29. They should have chosen i3 530-540 as unlocked dual because those cheap are the only ones that might be even remotly affected by low BLCK on bad mobo.

  30. I got all excited when I saw unlocked procs from Intel. Sadly I’m very disappointed by the ones they picked. If it had been an unlocked i5 750 I would be reconsidering getting an AMD build. I’m not a big overclocker, I don’t usually like to mess with it but having an unlocked multiplier makes it easy for me to do without any real hassle. I like that, quite a bit.

  31. Robert Reynolds

    Perhaps this is Intel just test marketing the concept, giving the consumer another reason to look at a couple of CPUs that might not sell well. Also, Intel might still be worried about jackasses”remarking” Intel processors so will monitor what occurs the situation with a small, limited roll out of unlocked CPUs. Maybe a hint of more things to come in the future as we all would like seeing CPUs that are special and different in some way than the norm appear once in a while.

  32. The 600 series unlocked processor is just begging to be “remarked” and sold to businesses with its integrated video. Is Intel trying to reprove their point?

  33. Van Halen lover

    terrific. i’ve been on pins and needles for months waiting for an unlocked s1156 cpu. Yay !!!

  34. Where the crap are the 1366 unlocked chips? why ignore your “enthusiast” socket with something that is most certainly an “enthusiast” feature?

  35. I’m really pleasantly surprised that the 2.93GHz Core i7 875K at $342 is cheaper yet has more features than the 2.93GHz Core i7 870 at $562. Although I’m guessing that’s only temporary as the upcoming 3.06GHz Core i7 880 will probably take over the $562 price point, with the Core i7 870 dropping down to $284 and the Core i7 860 being phased out. There’s also a Core i5 760 to replace the Core i5 750.

  36. It feels like Intel is starting to make sure AMD knows their place, back down in the low budget market.
    I think 1090 sales are going to plummet now, 1055 should still be in the clear though.

  37. good review =D taught me things i didn’t know about

  38. Christian walker

    nice…love the air cooling results. 655 is a beast lol

  39. I don’t really understand the logic of having the unlocked processor much cheaper than the locked one. This is not a complaint as a consumer, but who in their right mind would even entertain the thought of getting the locked one? Good luck trying to sell a locked 870 for anything near what you paid for it (retailer or early adopter). I realize that early adopters take these risks, but this seems quite strange to me.

  40. So is it worth for me to sell my 860 for an 875K? Im almost thinking so…

  41. Not having dealt with OC on the i7/i5 chips, I had initially thought that unlocked multis wouldn’t really make a difference, but then I thought back to the fight many folks have with hitting a OC wall with them and thought differently.

    For those of us not completely familiar with OC’ing on these platforms, does it make the OC process a lot less painful?

  42. so you folks think pricing is not aggressive enough for its intended audience?

  43. I don’t think so as there were already Intel chips on the market for less than these are being offered for. If I’m reading the review correctly, the dual core might be interesting because of the new (possibly better clocking) stepping, but it’s basically a $40 premium for an unlocked core on an already existing chip.

  44. I have both an 860 and a 661 and in my opinion 860 is still the best bang for the buck for that price range. 875 is going to kill 870 but it is nearly $100 more than 860 for probably the same OC result. I might consider a 655 over a 660 or 661 but even still I would need some evidence that it would get me some extra mhz to bother paying the extra $40 or so. Just my 2 cents from an enthusiast perspective, not sure what a mainstream user will think about unlocked.

  45. Most of the reviews I checked don’t even overclock the chip (if they tested it at all) and the ones that did (legit reviews, anand) don’t even end up adjusting the CPU multiplier anyway, they only adjust the other multipliers on the chip (memory for example) which are unlocked on all Core i5s/i7s, not just the new Ks. great job guys

  46. I’m still gaming on a Q66 @ 3.6GHz which in benchmarks comes just short of i7 920’s.Got no real incentive to upgrade, the only problem I’ve had with it was that GTA IV chokes on anything other than i7’s

  47. Yeah thats my plan as well. I have my q9550 clocked in at 3.8ghz and it is more than enough for what I need. I built my rig for dirt cheap a little over a year and a half ago when the i7’s were just released. A more energy efficient chip would be nice though but its 95 watts is nothing compared to what the nvidia gtx 280 uses that I have in it.

  48. Still looking forward to the Sandy Bridge B2.

  49. Not as awesome as it sounds – the 870/875K are the overpriced parts, the 655K is only a dual core. This would actually be useful if they did unlocked versions of the 750/860/930 – i.e. the mainstream quad-cores.

  50. Great Intel finally offered something inline with the AMD Black line. An unlocked CPU that isn’t price north of 1K that’s sheer madness! However I do see that they still protected their crown jewel i7 980X by making these both LGA 1156 chips. If you want enough lanes to run a decent dual card SLI/Crossfire setup you will want x58 and the higher priced CPU’s that come with it.

  51. Every time I see an article about Intel, all I think is that those MFers are purposely delaying USB 3.0 acceptence which delays USB 3.0 device selection as well. Dang you!

  52. Pretty much any Core i7 is significantly faster and more efficient than the Q9550.

  53. way to go intel….

  54. So far, I’ve been slightly disappointed with the Core i7-875K after reading reviews from the usual hardware sites that I visit. I do like the price though.

  55. Wow after reading the mess that anandtech put up today this review is a masterpiece

  56. Intel did release the E6500K for the LGA 775, but only in Asia.

    The only good thing here is that these chips will probably ship with heat sinks that don’t suck and a good price drop for the i7 870. Otherwise, who cares, FSB stability on decent P55 boards has not been a problem. What the socket really needs from Intel is a better chip-set, not easier overclockers.

  57. wow now that is some serious over-clocking… and here i am trying to push my 955 up past 3.93. i would have liked to see some liquid cooling tossed in to spice things up and maybe one more 5970… great job Chris!

  58. The only good thing here is that these chips will probably ship with heat sinks that don’t suck and a good price drop for the i7 870. Otherwise, who cares, FSB stability on decent P55 boards has not been a problem. What the socket really needs from Intel is a better chip-set, not easier overclockers.

  59. LGA 1366 i7 hopefully will be available soon. GRRRRRRRRR……..

  60. Intel makes good cpus, that’s a given. Their problem lies in the pricing of such chips. I mean if you could buy a processor because you want to overclock it then the locked but cheaper one is as good as the unlocked one. Sure, it’s more difficult, but I for one love a challenge.

  61. 1055t at 4Ghz here!!

    For only 200bucks I got my 1055t to 4Ghz!!
    1.445v 32c Idle, ~53c Load

    My ~$1000 rig…maybe a little more.

  62. Wonder why 875K is not a 32nm upgrade, we could see some serious overclocking at low power consumption.Still waiting for affordable (for me)pure processors without graphics with 4/8 cores on 32nm.

  63. Finally, very good news for serious desktop processing power that wont leave me with an empty wallet. The 875K is going to be my next CPU for 3D modeling and rendering. I hope it will keep me entertained for a while =)Don’t get me wrong but I was getting bored with the tiny world of ARM and Tegra and on the other side of the spectrum the hexacores and dual Xeons were far and away for my budget.

  64. it’s obvious that intel doesn’t unlock the i5 750 and 930 for precise the reason stated: they are way to popular to upgrade to unlocked versions that will effectively cancel all orders for the normal ones prolly. Although very good oc, the i5 655 is a dual core and in these times I want a triple core minimum for multitasking and rarring, videoeditting and such. Pure gamers could use a fast dual core though.
    good article and very nice oc’s on all cpu’s. The six core still disapoints me a bit in performance, I would have expected more power from the two extra cores. Now it only matters in the specific multicore/thread optimized programs which are not that abundant.

  65. glad to see intel playing ball with us 🙂 like I often put it: the empire always strikes back. I cant wait to see how AMD will respond to this new chips.

  66. I think the X6 returns to the original Phenom’s independent core clocking system, albeit with much quicker ramp and slam delays (I think those are the terms?). Thus, it’s very elegant and results in a far smaller performance drop than we saw back with Barcelona. If you throw something relatively heavy at the Phenom II X6, you wouldn’t ever notice a difference between having all cores locked at the same frequency and all cores working independently anyway.

  67. same old price structure by Intel, quite perfect though so as not to affect the value other chips.
    anyways, new parts won’t sway me from buying the AMD black editions. there’s not much performance difference.
    the savings will get me a reasonable a heatsink.

  68. Darn, I can’t wait for unlocked Sandy Bridge. Intel should unlock all its processors but put a pop-up on boot so venders won’t sell overclocked computer as highend PC.

  69. Nice review and good conclusion. My eyes popped a little at the power consumption of the i7-875K _ SHIIIIIIIIIITTTTTTTTTT

  70. I think this article shows that hyper-threading is definitely not the same as additional physical cores. But it sure helps a dual core compete with similarly clocked quads.

  71. Thanks for including a few mainstream benchmarks, especially Adobe photo processes. Much appreciated.

  72. Sad to see how much AMD current processors really lag behind Intel. But even though AMD processors get owned easily when comparing core to core all my computers are still AMD. Intel really shoots itself in the foot with overall platform costs. Knowing how much cheaper and more full featured the AMD platform keeps me coming back every time.

  73. Love the articles. Please, keep ’em coming.

  74. very well written entertaining, indepth and enough info to base a purchase on.

    875k is on my wish list.

  75. very well written entertaining, indepth and enough info to base a purchase on.

    875k is on my wish list for sure

  76. hang on, is it just me or is it not possible those cpus would die in a short while at such high speeds?

  77. @ GARRY – no they would be fine, its temperatures you need to worry about especially under increased voltage. I think even 87c under load would be alright. they can take some punishment. personally though id take it down a bit long term, maybe 4.75ghz :p

  78. yeah the clock speeds have nothing to do with it. its voltages long term are the killer. its a little like lying under the sun for a while, the longer you do it the worse you end up becoming.

  79. Zardon I was hoping you would do this review, just got home. Excellent read, thanks. Wont be changing my black edition for a while, but really entertaining read

  80. these chips can sure as shit overclock, ill buy that for a dollar. or 500 even.

  81. these chips can sure as shit overclock, ill buy that for a dollar. or 500 even.

  82. Checking other reviews for 875k on the web and it’s quite sad to see how much some journalists struggle with overclocking. Has anyone seen anyone else score the big 5-0 GHz ?

  83. lovely stuff. nice oc’s and good work from intel. AMD need to catch up now. slotting in another 2 cores doesn’t always mean a victory either so take note !

  84. Insane overclocks. didnt think they could hit that on air cooling. Seriously though what the fuck is up with that cooler? its the same size as my garden shed.

  85. Thanks for the overclocking info Zardon, I can’t overclock this friggin intel mobo as the mechanics are just off the wall. its not like a standard board. I managed to get my 750 up higher by nicking some of your settings 🙂

  86. I was about to just give up. I went to look for Intel 875k reviews and after reading Anandtechs spelling mess and Hexus testing mess was going to shut the computer down in disgust.

    Have to love google for finding little sites like this , ive never heard of 🙂 excellent review, truly excellent. Will be back!

  87. Z is the man 🙂

  88. Excellent work Allan, came very close to just bashing a computer together myself based on these articles.